Resistor type flame detector



March 4, 1952 J DEUBEL 2,587,977

RESISTOR TYPE FLAME DETECTOR Filed NOV. 4, 1948 2 SHEETSSHEET 1 FIG. I

IO n

INVENTOR. l8 IZ JUSTIN A. DEUBEL m,ml Mm March 4, 1952 J DEUBEL 2,587,977

RESISTOR TYPE FLAME DETECTOR Filed NOV. 4, 1948 2 SHEETS-SHEET 2 INVENTOR.

JusTm A. DEUBEL BY Patented Mar. 4, 1952 UNITED STATES RESISTOR TYFE FLAME DETECTOR Justin A. Beubel, Hales Corners, Wis, assignor to Perfex Corporation, Milwaukee, Wis, a corporation of Wisconsin Application November 4, 1948, Serial No. 58,255

I 7 Claims. 1

This invention relates generally to thermal devices which respond to the presence or absence of flame and more particularly to a thermal device which responds immediately to the establishment of combustion in a heating plant and responds immediately to the cessation of (John bustion therein.

I In control systems for fuel fed heating plants it is customary to provide a flame failure saf guard in the system to shut down the heating plant in the event that combustion fails either at the beginning of or at any time during a normal operating cycle of the heating plant. Such flame failure safeguards usually comprise a switch which is operated by the initial movement of a temperature responsive element to the initiation or cessation of combustion. Since initial movement of the temperature responsive element operates the switch, provision must be made for permitting the element to continue to move after switch actuation in response to addi-- tional heating of the element and yet lie-actuate the switch immediately upon a reversal in direc" tion of movement of the element. This is onstomarily accomplished by use of a slip friction device wherein some portion of the mechanism is permitted to slip against a frictional force upon continued movement of the element in the same direction after switch actuation.

The principal object of this-invention is to provide an apparatus which, when wired into a suit-- able circu t, accomplishes electrically a flame detection function similar to that heretofore achieved by mechanical slip friction flame do" tector's.

A furt er ohiect of this invention is to provide a flame detector which accurately and rapidly responds to the presence or absence of flame by creat n a tem erature differential between t o tem erature responsive resistances when a flame is present an rapidly decre sing t is t mperature difierential when the flam is eutne ish d.

A further oh ect of this invention is to provide a flame detector apparatus which beca se of its small size is easily, and conveniently mounted within the influence of the flame in the combustion c amber of a heating plant.

Other ob ects and atten ant advantages will beappreciated by those skilled inthis art as t e invent on becomes better understood by reference to the following description when consid ered in connect on with the accompanying drawings, in which:

Fig. 1 represents a side View of an embodim nt of invention. a p rtion of a side wall broken away to show location of interior parts.

Fig. 2 represents a top sectional view of the device shown in Fig. 1, the section being taken generally along the line IIII of Fig. 1.

Fig. 3 is an end view of the device shown in Fig. 1'.

Fig. 4 is a diagrammatic showing of a circuit,

2 and switch controlled thereby, utilizing the device illustrated in Figs. 1, 2 and 3.

Fig. 5 is a side view, partly in section of a portion of an oil burner illustrating the position at which the embodiment of the present invention may be mounted.

Referring now to Figs. 1, 2 and 3 the flame detector l0 comprises a tube rectangular in crosssection formed by channel-shaped member H and a base-plate !2 which may be of brass or other metal having a good thermal conductivity. The forward end 13 of tube It is open, the other end I5 is closed by means of a block l6 formed of Bakelite or other insulating material.

A strip l1 formed of a metal such as stainless steel is secured at one of its ends to the baseplate [2 in good heat conducting relation therewith by any suitable means such as rivets iii. A copper block 19 is secured to the free end of strip I! by soldering or any other suitable means which provides for good thermal conductivity between strip I! and block l9.

A first temperature responsive resistance 2! is mounted on an intermediate portion of strip l1 and a second temperature resistance 22 is imbedded in block l9. These resistances are of a type having a relatively high thermal coefiicient of resistance. As illustrated, resistances 2| and 22 are of the thermistor type and have a high, negative thermal coeiiicient of resistance, that is, their resistance decreases at a rapid rate as their temperature increases as is Well known in the art. Thermistor resistances 2| and 22 may be of any suitable outer configuration: as illustrated, they are of the bead type. It will be understood that resistances 2! and 22 may he of a type having a positive thermal coefficient of resistance, such as wire wound resistances. the principal requirement which they must fulfi in regard to the present invention being that their resistance either increase or decrease rapidly with a temperature change.

Blade 23. 2d. 25 and 26 extend thro"gh the Bakelite block 16 and leads 2'! and 2! connect resistance 22 with blades 23 and 24 and leads 29 and 39 connect resistance 2| ith blades 25 and 26. Blades 23. 24. 25 and 26 are connected with a conduit 32 which serves as a connecting lead between the flame detector and the heating plant controlling circuit, as will subsequently be explained.

It will be understood that the circuit shown in Fig. 4 and its operation form no part of the present invention. Other circuits might be devised utilizing the. temperature responsive resistances 2| and 22, that shown being merely illustrative. Fig. 4 illustrates a portion of a circ"it utilizing the flame detector previously described. Transformer 33 has secondaries 34 and 35 hich serve as a power source for ener ization of t e circuit shown. Secondaryt l is connected across a resistance network 31 which comprises temperature The circuit shown in Fig. 4 operates generally in .the following manner: as long as resistances 2| and 22 are at the same temperature, the voltage output of network 3'! is such as to hold the control electrode 3| of tube 39 at a potential below the cut-ofi potential of tube 39. If a temperature differential exists between resistances 2| and 22, their resistances become unequal and the voltage output of network 31 is increased sufliciently to raise the potential of the control grid 3| to allow the tube 39 to conduct, energizing relay 36 and closing switch 42.

Fig. 5 shows the nozzle portion of a gun type oil burner which i illustrative of the type of apparatus with which the present invention may be used. A blast tube 45 serves as a passage for delivery of air for the combustion of oil particles delivered from nozzle 46 under pressure, the 011 being supplied through a central oil delivery pipe 48. Flame detector I9 is mounted in good heat conducting relation with a brass block 50 which in turn is held in good heat conducting relation with the pipe 48. Flame detector l and block 59 are held in place on pipe 48 by any suitable means such as metallic straps Block 50 serves only to space flame detector l9 from pipe 48 suiflciently to clear the obstruction to radiant heat from the burning oil ofiered by nozzle 46. Depending upon the dimensions of nozzle 46, block 59 may be omitted from the mountin arrangement. 7

With the flame detector mounted as shown in Fig. 5 and with resistances 2| and 22 connected in the circuit illustrated in Fig. 4 the operation is as follows: while the heating plant is shut down, resistors 2| and 22 are at the same temperature. and their resistances are substantially equal. Under these conditions, the voltage output of network 31 is insufficient to raise the voltage of electrode 3| to cause tube 39 to conduct, and relay 36 remains deenergized. When the heating plant is placed in operation, the oil delivered at nozzle 46 is ignited and a flame is maintained adjacent the end of blast tube 45. Radiant heat from the flame strikes resistor 2| and a portion of strip i 7 dlrectly, and rapidly heats resistor 2! to a temperature well above the temperature of resistor 22 which is shieldedfrom direct heat radiation. This temperature differential between resistor 2! and 22 causes their resistances to become unequal. increasing the'voltage of electrode 3| (Fig. 4) to cause tube 39 to conduct and the relay 36 to be energized thereby closing switch 42. As additlonal radiant heat is absorbed by strip H, the temperature of resistor 22 is also raised through heat conduction along strip H, but since strip I! has a good thermal connection with the relatively cool oil pipe 48 through block 50 some of the heat absorbed by strip I! is lost by conduction to the pipe 48, and, additionally, heat is radiated from copper block I 9. This serves to hold the temperature of resistor22 slightly below the: temperaresistance mounted on said body in heat conduct- 4; that shown in Fig. 4, holds switch 42 closed as long as a flame is present.

Should the flame be extinguished for any reason, the temperature of resistor 2| will immediately decrease since direct heat radiation from the flame will be cut off and strip i'i will lose heat by conduction through block relatively rapidly. Because of the large mass to surface area ratio of block 19, however, the temperature of block I 9 and consequently of resistor 22 will decrease relatively slowly. As a result the temperatures of resistors 2! and 22 will rapidly approach the same value and the temperature differential betweenresistors 2| and 22 will disappear.

This will result in the de-energization of relay 36 and opening of switch 42 relatively quickly after disappearance of the flame at the burner.

It will be noted that when coupled with a suitable circuit, such as that illustrated in Fig. 4, the flame detector embodying the present inven tion responds relatively rapidly to the initial appearance of a flame, is unafiected by continu ing increase in temperature of the flame detector while a flame is present, and responds relatively rapidly to the disappearance of the flame and the consequent decrease in temperature of the flame detector.

Various modifications coming within the spirit of the invention may suggest themselves to those skilled in the art and hence the invention is not to be limited to the specific form shown, except .to the extent indicated in the appended claims.-

ation from said flame through said open end of said casing, said first resistance being heated to a first temperature when flame is present in said combustion chamber, a body having a relatively large mass to surface area ratio and high thermal conductivity secured to said member and shielded from direct heat radiation from said flame by said member, a second temperature responsive ing relation therewith and adapted while flame is present in said burner to be maintained at second temperature defining a temperature dif tures; said casing, said member and said body forming a heat conducting path operating to rapidly decrease said tem erature differentia when said flame is extinguished.

2. An apparatus for detecting the presence or flame is present therein, a first temperature re sponsive resistance mounted within an open end a of said casing for exposure to direct heat radiation from said flame and heated to a first temperature when flame is present in said combustion cham-.

ber, a second temperature responsive resistancemounted within said casing in a positionshielded 1 mm.- direci he ad ates iron said e a body having a relatively large mass to surface area ratio and high thermal conductivity associated with said second temperature responsive resistance for maintaining a temperature differential between said first and second resistances while flame is present in said combustion chamber, said casing and said body operating to rapidly decrease said temperature differential upon extinction of said flame.

3. An apparatus for detecting the presence or absence of flame in a combustion chamber comprising: a casing adapted to be mounted in relation to said combustion chamber at a point the ambient temperature of which is below the temperature within said combustion chamber when flame is present therein, a first temperature responsive resistance mounted within an open end of said casing for exposure to direct heat radiation from said flame and heated to a first temperature when flame is present in said combustion chamber, a member having high thermal conductivity secured in heat conducting relation with said casing, a body having a relatively large mass to surface area ratio and high thermal conductivity secured to said member and shielded from direct heat radiation from said flame by said member, a second temperature responsive resistance mounted on said body in heat conducting relation therewith and adapted while flame is present in said combustion chamber to be maintained at a second temperature defining a temperature differential between said first and second temperatures; said casing, said member and said body operating to rapidly decrease said temperature differential upon extinction of said flame.

4. An apparatus for detecting the presence or absence of heat radiation com rising, a casing having an open end adapted to face the source of said heat radiation, a first temperature responsive resistance within said open end of the casing adapted to be exposed to direct heat radiation and heated to a first temperature by the presence of heat radiation; a member having high thermal conductivity secured in heat conducting relation with said casing; a body having a relatively large mass to surface area ratio and high thermal conductivity secured to said member and shielded from direct heat radiation by said member; a second temperature responsive resistance mounted on said body in heat conducting relation therewith and adapted while heat radiation is present to be maintained at a second temperature defining a temperature differential between said first and second temperatures; said casing, said member, and said body forming a heat conducting path to rapidly decrease said temperature differential when heat radiation is absent.

5. An apparatus for detecting the presence or absence of heat radiation comprising, a casing having an open end adapted to face the source of said heat radiation, a member having high thermal conductivity secured within said open end of the casing in heat conducting relation thereto; a first temperature responsive resistance mounted on said member in heat conducting relation therewith and adapted to be exposed to direct heat radiation, said first resistance being heated to a first temperature when heat radiation is present; a body having a relatively large mass to surface area ratio and high thermal conductivity secured to said member and shielded from direct heat radiation by said member; a second temperature responsive resistance mounted on said body in heat conducting relation therewith and adapted while heat radiation is present to be maintained at a second temperature defining a temperature differential between said first and second temperatures, said casing, said member, and said body forming a heat conductin path operating to rapidly decrease said temperature differential when said heat radiation is absent.

6. An apparatus for detecting the presence or absence of heat radiation comprising, a casing having an open end adapted to face the source of said heat radiation, a member having high thermal conductivity secured within said open end of the casing in heat conducting relation thereto, a first resistor having a relatively high, negative thermal coefficient of resistance mounted on said member in heat conducting relation therewith and adapted to be exposed to direct heat radiation, said first resistor being heated to a first temperature when heat radiation is present, a body having a large mass to surface area ratio and high thermal conductivity secured to said member and shielded from direct heat radiation by said member; a second resistor having a relatively high, negative thermal coeificient of resistance mounted on said body in heat conducting relation therewith and adapted while heat radiation is present to be maintained at a second temperature defining a temperature differential between said first and second temperatures; said casing, said member and said body forming a heat conducting path operating to rapidly decrease said temperature differential when said heat radiation is absent.

7. An apparatus for detecting the presence or absence of heat radiation and adapted to control an electric discharge device through a thermally created unbalance in a resistance network. said apparatus comprising, a tubular casing having an open end adapted to face the source of said heat radiation, a member having a small mass to surface area ratio and high thermal conductivity mounted within said open end of the casing and secured in heat conducting relation thereto, a first temperature responsive resistance mounted on said member in heat conducting relation therewith and adapted to be exposed to direct heat radiation, said first resistance being heated to a first temperature when heat radiation is present, a body having a relatively large mass to surface area ratio and high thermal conductivity secured to said member and shielded from direct heat radiation by said member, a second temperature responsive resistance mounted on said body in heat conducting relation therewith and adapted while heat radiation is present to be maintained at a second temperature defining a temperature differential between said first and second temperatures, said casing, said member and said body forming a heat conducting path operating to rapidly decrease said temperature differential when said heat radiation is absent.

JUSTIN A. DEUBEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,643,582 Martin Sept. 27, 1927 2,021,573 Alder Nov. 19, 1935 2,054,120 De Florez Sept. 15, 1936 2,139,504 King Dec. 6, 1938 2,305,507 Wilson Dec. 15, 1942 2,370,847 Dempster Mar. 6, 1945 2,490,534 Mesh Dec. 6, 1949 

